The present invention relates to optical devices and means for magnifying vision, more particularly, to telescopes, binoculars, telemagnifiers (binoculars that are closely focused to, and converge at a short distance), and the like. A Keplerian telescope comprises a positive objective lens group, hereinafter referred as xe2x80x9cthe objective lensxe2x80x9d, and a positive eyepiece lens group, hereinafter referred as xe2x80x9cthe eyepiece lensxe2x80x9d. In a typical telescope the objective and eyepiece lens groups produce an inverted image which require additional means for producing an erected image. The means for erecting the image commonly comprise a system of mirrors, prisms, or combination of both. It is well known to those skilled in the art that an image erection system should include an odd number of reflections in each one of the two perpendicular axes. The most common image erection system, used in field binoculars, employs the Porro-prism system or its light-weight mirror equivalent which is described in U.S. Pat. No. 4,488,790. Both of said Porro-prism systems have no mechanical left-right symmetry, and when a symmetry is desired one of several prism systems known in the art which typically include even number of planar reflectors in the plane of symmetry, and a single roof-reflector is usually employed. Typical examples are the Hensolt prism shown in FIG. 1a, and the Schmidt prism shown in FIG. 1b. A telescope employing a Schmidt prism is described in U.S. Pat. No. 4,795,235. Such telescope is relatively compact, however, since the Schmidt prism has no hollow equivalent it is relatively heavy for a given objective lens diameter. Another major disadvantage of a telescope of this type is the fact that the eyepiece and objective lenses are mounted at a relative angle of roughly 40xc2x0 between them. An additional drawback is the fact that the focal length of the objective lens is severely restricted for a given objective lens aperture, resulting in a relatively small F/# (the ratio between the focal length and the diameter of a lens). It is well known in the art that for a given set of system parameters the complexity of the optical design needed to achieve a given level of image aberration corrections is very dependent on the F/#. As a result, the number of optical elements needed for the objective and eyepiece lens groups with a small F/# is increasingly largexe2x80x94which impairs the compactness.
It was found that advantage can be taken of the cone shape of the light bundle emerging from a Keplerian telescope objective lens, in particular when its F/# is close to 3, by folding it in a manner analogous to that of the Hensolt prism. In contrast with the Schmidt prism that is inherently solid, relying on the total internal reflection, the present layout can be implemented by mirrors only, in order to decrease the total weight of the device. In addition, the angle between the optical axes of the eyepiece and objective lenses is optional. A Keplerian telescope including this optical structure seems to achieve the ultimate compactness possible for a given objective lens diameter, without compromising any performance parameter. This telescope may be used for compact monoculars, binoculars and, in particular, head-mounted binoculars and telemagnifiers.
It is an object of the invention to overcome the large size and relatively heavy weight limitations of the existing prior art telescopes by providing an alternative new, compact, and lightweight telescope structure.
It is another object of the invention to enable the use of the telescopes in some new applications, and to make the use of telescopes easier and more convenient in other existing applications.
It is another object of the invention to provide compactness in size and reduced weight without compromising any performance requirement.
It is another object of the invention to provide said adaptations to telescopes, monoculars, binoculars, and head-mounted telemagnifiers.
A telescopic device for magnifying image according to a preferred embodiment of the invention comprises a housing for including and supporting the optical components in suitable positioned relationship, the said housing having an eyepiece aperture and an objective aperture, and a space for including a folded optical path, an eyepiece group lens located along a first optical axis, an objective group lens located along a second optical axis, which is slightly displaced with respect to first axis, and an image erecting system comprising a first plane mirror, a second plane mirror, and a roof reflector.
A device according to a preferred embodiment of the invention has a first optical axis which is parallel to the second optical axis. According to another embodiment of the invention the device has a second optical axis which is tilted by about 20xc2x0 with respect to the first optical axis in order to provide a simultaneous view of the magnified and natural view.
According to another preferred embodiment of the invention, the optical components and the device housing are made from lightweight materials, and adapted to be head-mounted.
According to any embodiment of the invention, the optical components may include diffractive elements, the eyepiece lens of the device may have a substantially rectangular shape. Further, focusing means may be provided. Said focusing means may comprise at least one laterally moving reflector. Further, the focusing means are hermetically sealed.
A still another preferred embodiment of the invention may include means for compensating for accidental image jitters comprises pivot mechanism for at least oneplane mirror, at least one angular inertial sensor mounted on the telescope envelope, and a servo system for adjusting the plane mirror according to the data received from said inertial sensor, Said servo system comprises two electromagnetic actuators, and two capacitive deflection sensing means.